NEW YORK -- Serena Williams didn't watch any video of her loss to Ekaterina Makarova at this year's Australian Open as she prepared for their rematch at the U.S. Open.

She even hates looking at photos from defeats. But she is free to check out this match again after she won in straight sets in the third round Saturday.

Back when she used to relive those losses on tape, Williams said: "It was like stabbing myself."

No such pain so far at this year's U.S. Open. The fourth-seeded American won 6-4, 6-0, avenging her straight-set defeat in the Australian Open's fourth round.

The 42nd-ranked Makarova fell to 1-14 against top-five players.

When they played in January, Williams had seven double-faults and 37 unforced errors. The numbers Saturday were one and 16.

Agnieszka Radwanska, in her own words, survived her match. On a steamy day at Flushing Meadows, the second-seeded Pole was relieved to beat Jelena Jankovic in straight sets – and even that 6-3, 7-5 victory took 1 hour, 38 minutes.

"I was feeling like I was melting there," Radwanska said. "I survived the match. In the second set, I was just better for a couple of points."

She was broken four times, but Radwanska converted six of seven break-point chances against the 30th-seeded Serb.

While Radwanska is ranked a career-high No. 2 and coming off her first Grand Slam final at Wimbledon, Jankovic has fallen far from her No. 1 ranking in 2008 and hasn't been back to a title match at a major tournament since the U.S. Open that year. With confidence on her side, Radwanska knew patience would pay off.

"Especially with the hot conditions, you really have to fight more yourself than against the opponent," she said.

Jankovic had 37 unforced errors to 15 for Radwanska, who reached the fourth round at the U.S. Open for the first time since 2008. She has never been to the quarterfinals here.

"I think everything could happen today," Radwanska said. "So what I was trying to do, just fight 'til the end. Was a lot of the games that was like 30-all, 30-love, and then suddenly I was winning the games. It was a lot of weird points."

And a lot of long rallies, which both players tend to produce. On Saturday, they had six of at least 20 shots.

"We always have to run a lot in our matches, for sure," Radwanska said.

Nicolas Almagro, seeded 11th on the men's side, beat American teenager Jack Sock 7-6 (3), 6-7 (4), 7-6 (2), 6-1 to reach the round of 16 at Flushing Meadows for the first time.

Martin Klizan, who upset fifth-seeded Jo-Wilfried Tsonga in the second round, extended his best Grand Slam run by beating 32nd-seeded Jeremy Chardy 6-4, 6-4, 6-4. He next faces 17th-seeded Kei Nishikori, who defeated 12th-seeded Marin Cilic in four sets.

Other top players on court Saturday include Roger Federer and Andy Murray. Americans Sloane Stephens, James Blake, Mardy Fish and Sam Querrey are also scheduled to play.